THE jewel in Helensburgh's visitor crown is set to be covered by a giant enclosure almost 60 feet tall for up to 10 years.

The National Trust for Scotland is submitting a planning application this week for what it calls "a colossal yet sublime" enclosure to protect the Hill House from the weather.

The Trust says the see-through structure – with a solid roof on top and a metal mesh around the sides – will protect the building and keep the elements out, giving conservation teams the time needed to find long-term solutions to secure the building's structural integrity.

The plans, revealed this week, also include a ramped walkway between the structure and the house, giving members of the public the chance to see the conservation work up close – and stairs and a gangway over the top of the building, giving a bird's eye view of the house and opening up spectacular views over the Firth of Clyde.

Simon Skinner, chief executive of the NTS, said: “As our president, Neil Oliver, put it, the Hill House is in danger of ‘dissolving like an aspirin in a glass of water’.

"We are building what amounts to a shield around and above the Hill House to keep wind and rain out and give the building a chance to dry.

“The structure is effectively a porous cage, albeit a beautifully designed one, that still allows some movement of air and a degree of moisture penetration – this is essential to ensure the walls do not dry out too quickly and crumble as a result."

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